Radio receiving circuit



P J SNIDER RADIO RECEIVING CIRCUIT Filed June 25, 1932 Aug. 20, 1935. I

FHUL/ J SNJDER Patented Aug. 3 e r i v j. v

UNITED" STATES PATlilNT-j Q'F-FlfiE I 2,011,941 V RADIO RECEIVING CIRCUIT Paul J. SnidrfPlain city, ohidessignonwby mesneassignments, toitadio Corporation of y America, New York, N. Y., a corporation-of Delaware Application June 23, issasenai No. 618,867

,12 Claims. (crest-20) This invention relates to a radio receiving cirthe circuit of a converter that involves the novel .cuit, and more particularly to a circuit utilizing features of the present invention. r improved coupling means, which coupling means With particular referencev to the drawing, a V is adaptable to multi-range receivers capable of switch Iii has an arm 26 and a ii111ra1ity'0f00hi ii r eceiving signals in any one ofseveral wavebands. tacts l2, l4, I6 and H3. The contacts l2, l4 and 5 g In. the usual type of circuit, the detector and 6 ere-connected the e s of a ee ifl oscillator tubes are magnetically coupled. That and Z4 p y-r The th ends o t e is, a pick-up coil is used to pickup the oscillating e s fl, 22 are Connected to t energy from the oscillating circuit that is to be and t0 grellhd-at Ah antenna 1 i o n c mixed with the signal energy. This is an u'nde-l to th wi h rm so tha y chan in the 10 'sirable feature, because an extracoil is necessary, Position Of the flfi the a t y be 1 and beside thatgwhere signals are to be received nected to any of t e ce l5 in several different wave bands, extra pick-up The ihdllctehces 2 nd 24 are e a y t coils are necessary for each set of coilsused for eeupled h induct-ewes 39 and e I 'awave band, or if a single'pick-up coil-is used, duetances 28, 39 and 32 have their ends con- 5 there is difiiculty in obtaining the proper cou-, neetedtegethelend to ground M2, The other pling between the pick-up coil and the coils for ends of the in ductances 28, 30 and 32 are conthe diiierent wave bands. Also, with a system contacts en 33 respectively, of which utilizes a pickup coil, it is more difiicult a Switch 40. The switch 441 haSJan arm 42 con to completely and properly shield the 'units of the neeted 1' an i p control eM a 20 circuit. s thermionic detector tube 46, and capable of con- It is therefore an object of this invention to m y One Of ae s 6 and prgvide an im roved coupling system for use in a A variable condenser is connected to the switch radio receivin circuit, and particularly adaptable arm 42 nd to r nde 2. An a j able c n- .to a receiver that is to be usedforreceiving sigdenser -58 is-connectedacross the variablecon- V nals in a plurality ofwave bands, denser M. A shield 52, grounded at 2, encloses Another object of this invention is to provide a the sindlletahees ,1 39 an 3 h h 7 coupling system for a radio receiver which lends w tches and. p j j itself readily to the changing of 'Wave bands The thermionied tube 46 besideithe through the use of a switching mechanism. 'eentrel er'input r d a anode r outpu -30 Another object of this invention is to provide electrode y Screen'grid 6, a a e 53 a d a means for preventing interlocking of detector ah e rth h de 1' Ou pu elecand oscillator circuits, that is, to prevent the tun- '0d is Connected 1 male fr q y ChOke ing of one of the circuits from appreciably afiect- 62 and to one side of an adjustable condenser 64.

ing the tuning of the other. The other side of'the adjustable condenser 64 is 35 7 Another object of this invention is to provide nn t n inp r pr y inductance 68 a band switching system for a radio circuit'which of a Succeeding dio amplifying device th o permitsthe selection of various wave bands. a condenser 66. The-contact I8 is connected to Another object of this invention is to provide a t inductance 68 intermediate t-i d c e band switching system for a converter circuit and the condenser 6- The ee s tti n-- 40 which permits the selection of various wave bands nectedto a terminal 70 through s or 2- by the converter, or the use of the receiver, with The a or tP e1e9tmde also which theconverter is ,connected, without the nectedto P termmal reu h k ir ctnifiiifii12'eitiitii tfiicl oi ttifitfai Anobper obvlect of thls mvfmtwn is to provide for supplying the potentialstothescreen grid 56 i an emclent. mains for gouphng the output and anode 54. A condenser 80 connected'to the converter circuit to the input of a radioreceiver. screen grid, 56 anditoy ground at by; Further obJects and advantages of the'present 7 pass for alternating current from the screen grid.

invention will be apparent from theif-ellowing f The heater'li!) is provided with leads 16"and 18 5o scflptim reference e n had to the accompany" forconnection to a suitable source of heating ing drawing wherein a preferredembodiment of current; i

one form of the present invention is clearly shown. e cathode 5 is connct'ed to an a mf n h win i switch 84. Contacts 88, 90 'and 92, w ith which p The figure discloses a'schematic diagram" of the arm 86 'may connect, are connected to ends 55' across that resistor.

ciated, is connected to one side of a? condenser I22 and to oneside' of a variable condenser I24.

The other side of the condenser I22 is connected to a control electrode E26 of a thermionic oscillator tube i223, and the other side of the variable condenser A shield i 32 encloses the inductances 94, 96, 98, IE6, IE8 and iii], and the switches 84 and I20, which shield E32 is-grounded at N32. The thermionic oscillator tube I28 has in addition to'the control electrode it; an anode I34, a cathode I36. and a heater I 38. The control electrode I25 is connected to the cathode I36 through a resistor i453, and thence is grounded at I452. The heater I38 is aprovided with leads i i l and I46 for-. connection to a suitable source of heating current. The anodeIMis connected'to the terminal I9- througha; resistor I48. and a resistor 3 14, whichresistorsare.connected inseries. One

side of a condenserltiil is [connected to a com mo-n terminal of. the resistors I4 and I48 and the choke fitand to ground at I52. A condenser 15A has one side connected to'the anode I34 and the other side connected to the switch arm 88 of the switch B l. The variable condensers 124 and are indicated asbeing controlled from 'a common control element I55. The switches 84', I20, 40, and ID are indicated as beingcontrolled by a commoncontrolelement I58;

The input or primary inductance 53 is magnetically coupled with a secondary inductance I65 toform a coupling device I62 Anend of the inductance 63 is connected to an end of the inductance I60 andto ground. at I64. A variable condenser I66 is connected across the secondary inductance I65! to tune that inductance to resonance at any desired frequency. The dashedline I'I!) indicates that the couplingdevice 92 and the apparatus which succeeds it may be in a separate unit from the apparatusfiof the. circuit previously explained. In fact, if the circuit disclosed is utilizedas ashort wave converter, 'for which it is especially adapted, the coupling device I62 may be the input circuit of a' conveh-- tional broadcast receiver. a

The primary inductances 20, 22 and 24 are of I different sizes; and each is magnetically coupled to one of the secondary inductances 28,39 or 32, and they are so matched in coupled pairs that when a particular secondary inductance is connected in. the circuit by the switch 40, and the proper. primary*isselected by the switch I9, the proper coupling ;will;- befprevidedior the frequency band coverable by the secondary. and the variable condenser 48.- The signals are picked up on the antenna I-and' transmitted to the pri- Inary inductance to which theswitch arm 26 is connected, or. directly to theprirnary of the coupling device I62 through the contact I8.; ,When the signals are transmitted to one of the primary .indu'ctances 29,. 22' or 24, they are. in, turn transmitted toa secondary inductancegto which the arm 42 of the switch 140.. sv connected, Since the I25 is connected tor'ground at I30.

:plied to-the control electrode id.

preferably set so as t oproduce sc variable condenser 8 tunes the secondary thatv is being used, to, resonance at the signal freof the oscillator tube I28. Each one of the oscil- Iator tuning inductances we, I98 and iii] has anassoci'atedfeed-back or ticlrler inductance electromagnetically coupled therewith. The action of the feed-back or ticklerinductanccs 54, SE and 88, coupled with the anode 55 i oi the oscillator tube I28, tends to cause the tube 28 to oscillate. Since it is desirable to have diiferent sizes of tickler inductances for different sizes of oscillator tuning: inducta'nces, the'switch provided toselect the proper ticlzler induc- 'tance to operate with the oscillator tuning inductance selected by the switch I29.

The D. C. biasing potential for the detector tube is applie-dbetween the control or input elec- =trode =i-andthecathode-58 by virtue-of the D. C.

drop inpotential across the resistoriaid. This potential is applied to the cathode .53 through the holder inductance that, is selected by the switch 8 3.1 Since the cathode 58' is directly coupled to the anode circuit of, the oscillator tube I28, oscillating energy is a plied to that'element -of the detector tube at the same time the signal designing the variable condensers 48 and 24 the inductances which those, condensers tune, as well as adjusting the condenser 55 to the proper valuathe resultant output frequency in'the cirfcuit of theanode 54 may be kept constant regard- -less of the frequency of the signai being received. The condenser I54.- preventsgthe potential of the ,anodei34 from beingfapplied'te the cathode By properly The resistor Ml! connected between the control a d an 5'5 are 3 e i so chosen that a high gain may produced between the detectortube the succee Ling plifying unit. The adjustable som e at theoutput frequency, in the anode circ of thefldetecuor tube 65. Theoutput signals. the anode 54 of the detector tube are thus applied to the input'of an amplifying, detectr reproducing device especially constructed for use with the oscillatorvandi detector disclosed, or to the input terminals of a conventional type radio receiver. -11 the oscillator and'dete'ctor unit is "used with a succeeding unit which by I itself is capable of thereception of signals, the oscillator its effectupon its signal reception by'causing the ,and detector unit may be rendered inoperative in and 88 are controlled by acommo-n control element as indicated by 558, the switching of frequency band may beaccomplished by a single switching operation, i i

It isa common diificultyexperienced inthe design ofacircuit such as the one disclosedfand using the heterodyne principle of operation that the tuning of one of the tunable circuits will tend .to influence tuningof the other one. Ihis action or phenomena iscommonly called interlocking. The interlocking action tends 'to'jbeeven .more prevalent in acircuit utilizing direct coupling such as that in the present circuit. However, it has been found that by shielding the primary and secondary inductances from those associated with the oscillator, and by keeping the value of the resistor hit as high as possible, this interlocking action maybe avoided. a

'While the form of embodiment invention as herein disclosed, constitutes a preferred form, it, is to be understood that other forms might be adopted,- all coming within the scope ofthe claims which iollow:

'the latter througha range of local oscillationfrequencies, a non-reactive path directly connecting the cathode ofv said detector tube to the said reactive pathwhereby local oscillation en- .ergy produced in the local oscillator is impressed -on the detector solely through said non-reactive fpath, said reactive path including a reactance of high impedance todir'ect current, said last reactancebeing connectedbetween the oscillator tube anode and said non-reactive path.

. '2. 'In a lhjet erodyne receiver system, a first detector tubepa local oscillator tube, a signal collector,.means for coupling said collector to the signal control electrode of saiddetectortube, a variable condenser, connected to the said electrode, for tuning the coupling meansthrough a desired signal, frequency range, a reactive path regeneratively coupling the anode and control grid circuits of. said oscillator tube, avariable condenser. in the:oscillator grid circuit for tun- .ing the latter through a range of local oscilla-- tion frequencies, a non-reactive path directly connecting the cathode of said detector tube to the said reactive path whereby localoscillatime energy produced in the local oscillator is impressedon the detector solelythrough said nonreactive path, said reactive path in'cludinga reactanceoi high impedance'to direct current, said last reactance being connected'betwe'en the.oscillator tube anode and saidnon-reactivepath, and

means for shielding said collector coupling, means ifromsaid reactive coupling path.

, i In a heterodyne receiver system, a first deof the present .tector-tube, a'local oscillator tube, a signal collector,;rneansfor" coupling said collector to the signal; control electrode ofgsaid detector tube, a

yariable condenser; conne'ctedto the said elec- .trode, for tuningthe coupling means through a desired signal frequency range, a reactive path 'regeneratively coupling ,the anode and control 7 grid circuits oi saidjoscillator tube," a variable jcondenser in the oscillator grid circuit, for tuning the latter-through a, range of'local oscillation ire 1 quencies, a non-reactive path directly connecting the, cathode of said detector tube to the said reactive path whereby local oscillation energy produced in thelocal oscillator is impressed on the detector solelythrough said non-reactive path,

said reactive path including a reactance ofihigh impedance to direct current, said last reactance being connected between, the oscillator tube anodeand saidnon-reactivepath, means for shielding the collector coupling means from said're active-coupling path, anda resistor of high mag nitude connected between the control-grid and adjustment of one of. said variable condensers from affecting the tuning'of the circuit associated'with the other variable condenser;

4. Ida heterodyne receiver system, a first'deteotortube, a local oscillator tube, a signal col- 1e'ctor,rneans;for coupling said collector, to "the signal control electrode of, said detectorptube, a variable condenser, connected tothe said electrode, for, tuning the coupling means through a desired signal frequency range, a reactive path regener'atively coupling the anode and control grid circuits of said oscillator :tube, a variable condenser injthe-oscillatorgrid circuit for tuning the latter through a range of local oscillation frequencies, a non-reactive path directly connecting the'cathode of said detector tube to the saidreactivepath whereby local oscillation energy produced in the local oscillator is impressed on the detector solely through said non-reactive path, said reactive path including a reactance of high impedance to direct current, ,saidlast reactance being connected between the'oscillator tube anode and said noni-reactiyepath, 'aresonant circuit, tuned to the beat irequency following said detector tube; anda series-resonant path, tuned to said beat frequency, couplingithe anode circuit of said detector tube'to said resonant jcircuit. 1

5. In a heterodyne, receiver system,- a first detectortube, EL'lOQSl oscillator tube, a signal'cole lector, means for coupling sai'dcollector to the signal control electrode of said; detector tube, a

-variab1econdenser, connected to the said elec- ,trode', for tuning the coupling means through a desired signal'frequency range, a reactive: path regeneratively coupling the anode and control Fgrid circuits of said oscillator tube, a: variable condenser in the oscillator grid circuit for tuning :the latter through a range of local oscillation, fre- ',quencies,- a non-reactive path directly connecting {the cathode fof said detector tube to the said re .active path whereby local oscillation energy proandjsaid non-reactive path, said collector coucathode of. said oscillator tube for preventing plingmeans consisting of a plurality of pairs of lector andsaid detector: signal control electrode.

6. In combination, a local oscillator stage including a tube, a plurality of pairsof magnetically coupled coils, a switch for selectively connecting a desired one of said pairsito the oscillator control grid, a second switch for selectively connecting said-desired pair to the oscillator anode, a variablejcondenser for' tuning the oscillator through a range of oscillation frequencies,,afrequency' changer stage including a tube, asignal collector, a plurality of coupling reactances, switch means for selectively connecting a desired one of said coupling reactancesbetween said collector and the input electrodes of the changer tube, a variable condenser for tuning the selected coupling reactance through a signal frequency range, means for simultaneously adjusting said two switches andsaid switch means, means for simultaneously adjusting said variable condensers and a direct connection between the frequency changer cathode and the said second switch for impressing the local oscillation energy upo said frequency changer. '7. In combination, a local oscillator stage in- -cluding a tube, a plurality of pairs of magnetically'coupled coils, a switch for selectively connecting a desired one of said pairs to the oscillator control grid, a second switch for selectively'connecting said desired pair to the oscillator anode, a variable condenser for tuning the oscillator through a range of oscillation frequencies, a frequency changer stage including a tube, a

a signal collector, a plurality of coupling reactances. switch means for selectively connecting a desired one of said couping reactances between said collector and the input electrodes of the changer tube, a'variable condenser for tuning the selected coupling reactance through a signal frequencyrange, means for simultaneously adjusting said two. switches and said switch means, means for simultaneously adjusting said variable condensers, and a direct connection between the frequency changer cathode and the said second switch for impressing the local oscillation energy upon said frequency changer and a series resonant network, tuned to the operating beat frequency, connected in the frequency changer out- 7 put. 1 l

8. In combination, a local oscillator'stage including a tube, a plurality of pairs of magnetical-v ly coupled coils; means for completely shielding said coils, a switch for selectively connecting 'a desired one of said pairs to" the oscillator controlI grid, a second switchfor selectively connecting said desired pair to the oscillator anode, a variable condenserfor tuning the oscillator through; a range of oscillation frequencies; a frequency changerstage including a tube, a signal collector,

a plurality of coupling reactances, switch means for selectively connecting a desired one of said coupling reactances between said collector and the input'electrodes of the changer: tube, a va-- riable condenser for tuning the selected coupling I, reactance through a signal frequency range,

means for simultaneously adjusting said two switches and the switch means, means for simultaneously adjusting said variable condensers, and a direct "connection between the frequency changer cathode and the said second switch for impressing the local oscillation energy upon said frequency changer. Y

' 9. In combination, a'local oscillator stage: in-

cluding a tube, a plurality of pairs of magnetically coupled coils, a switch for selectively connecting a desired one of said pairs to the oscillator control grid, a second switch for selectively connecting said'desired pairto the oscillator anode, a directcurr'ent blocking condenser between the secondiswitch and the oscillator anode, a variable condenser for tuningthe "oscillator through a range of oscillation frequencies, a frequency changer stage including a tube, a signal collector,

a plurality of coupling reactances, switch means for selectively connecting a desired one of said ccupling reactances between said collector and the input electrodes of the changer tube, a variable condenser for tuning the selected coupling 'reactance through a signal frequency range,

means for simultaneously adjusting said two switches and the switch means, me'ans'for simultaneously adjusting said variable condensers, and a direct'co'nnection between the frequency changer cathode and the said second switch for impressing the local oscillation energy upon said frequency changer.

10. In combination, a local oscillator stage including a tube, a plurality of pairs of magnetically coupled coils, a switch for selectively connecting a desired one of said pairs to the oscillator control grid, a second switch for selectively connecting said desired pair to the oscillator anode, a variable condenser for tuning the oscillator through a range of oscillation frequencies, a frequency changer stage including a screen grid tube, a common source of positive potential for the anodesof both tubes and the screen grid of the changer tube, a signal collector, a plurality of coupling reactances, switch means for selectively connecting a desired oneof said coupling reactances between said collector and the input changer,

11. In combination, a local oscillator stage ineluding-a tube, a plurality of pairs of'rnagnetically coupled coils, a switch for selectively connectinga'desired one of said pairscto the oscillator control grid, a second switch for'selectively con necting said desired pair to the oscillator anode, a

variable condenser for tuning the oscillator through a range of oscillation frequencies, a fre quency changer stage including a'tube, a signal collector, aplurality of coup-ling reactances, a switch for selectively connecting a desired'one'of said coupling reactances between said collector and the input electrodes of the changertube, a

variable" condenser for" tuning the; selected coupling reactance through a signalfrequency range, means for simultaneously "adjusting said switches, means for simultaneously adjusting said variable condensers, a condenser in theconnection betweenthe first switch and the oscillator grid, and a resistor of high magnitude connected between the oscillator grid and its cathode, and

a'direct. connection between the frequency changer cathode, and the said second switch for impressing the local oscillation energy upon said frequency changer, ,Y V

.12. In combination, a local oscillator stage including a tube, a plurality of pairs of magnetically coupled coils, a switch for selectively connectinga desired one of said pairs to'the oscillator control grid, a second switch ifor selectively connecting'said desired pair to the oscillator anode, a variable condenser for tuning the oscillator through a range of oscillation frequencies, a frequency changer stage including a tube, a signal collector, a plurality of coupling reactances, means for completely shielding said coils, and additional means forcompletely shielding said coupling reactances, a switch for selectively connecting a desired one of said coupling reactances ing the selected coupling reactance through a signal frequency range, means for simultaneously adjusting said switches, means for simultaneously adjusting said variable condensers, and a direct, connection between the frequency changer cath- PAUL. J. SNIDER. 

